Well monitoring system

ABSTRACT

A monitoring system for monitoring resources such as water in a bore having an air column extending from a wellhead to a surface level and a resource column extending from the surface level to an extraction inlet includes a sensor unit and a base unit. The sensor unit includes a sensor mounted within the bore and including a transmitting unit for transmitting at least a single sound pulse formed of a pulsed sinusoidal waveform into the bore and a receiving unit for receiving a return signal representing the single sound pulse reflected from the water surface level. The base unit uses the measured round trip time to determine an air column length from the sensor to the water surface level and a water column length from the water surface level to the extraction inlet and, from a cross sectional area of the bore, a water resource value representing a volume of water contained between the water surface level and the extraction inlet. The base unit may also determine resources values such as a current water level, a static water level, a highest recorded water level, a lowest recorded water level, a water level trend, a usage rate, and a recovery rate, and may generate alarms for various values.

FIELD OF THE INVENTION

[0001] The present invention relates to an apparatus and method for monitoring the state of wells and, in particular, for monitoring resource levels, usage, reserves and trends in one or more water wells of a water system and, for example, alerting users of low water resources and manually or automatically controlling water usage and the operation of water systems according to the availability and recovery rate of water resources and the relative priority of water uses.

BACKGROUND OF THE INVENTION

[0002] Increases in the demand for water supplies due to increases in populations and population densities and other increased uses of water, such as increased demand for agricultural production, have made the efficient management of water resources a matter of primary importance. The efficient management of water resources and the efficient use of water systems in turn requires an effective means for monitoring water usage and reserves and for monitoring trends in water usage and reserves, including resource replenishment rates.

[0003] The problem of resource monitoring is of particular importance and difficulty in regions where wells are a significant source of water, or even the primary or sole source of water. Wells are a significant or primary source of water for users ranging from private residences to major cities and major agricultural areas and in extensive regions ranging from apparently well watered temperate zone areas where usage exceeds surface water supplies to marginal or desert areas that could not otherwise support any significant population or agriculture or that would otherwise be marginal or even desert zones capable of supporting no more than minimal human or plant life.

[0004] Underground water sources such as wells, however, and unlike rivers, lakes, reservoirs and other surface sources, are difficult to observe directly. As a result, it is very difficult to determine and monitor the levels, amount of reserves and depletion and replenishment rates of underground sources, so that needed resources may go unused or limited resources may be degraded or exhausted.

[0005] It should also be noted that the need for effective resource monitoring also extends to the operation of the wells themselves and to the operation of associated water extraction systems, such as pumping systems to raise the water from underground to where it is to be used. For example, over extraction from a well, perhaps to the point of pumping the well dry, may result in collapse of the well or of the sources feeding the well or the infiltration of contaminants or sediments into the well or the water table, such as dirt, contaminated water, such as surface water or salt water, or natural or man-made chemicals, and so on. Also, extraction to the point that the pump, for example, is not drawing or pumping water can result in loss of prime in the pump or, because most pumps depend upon the pumped water for lubrication or cooling, the pump may overheat or otherwise suffer excessive wear or damage.

[0006] It will be appreciated that the above problems are compounded in the relatively common situation wherein a water system, whether for a private residence, community or agricultural area, is comprised of multiple wells and, consequently, multiple pumps and the associated piping, valves, reservoirs, and so on. In many instances, and for example, it is necessary to allocate or rotate the usage load among the wells according to such factors as capacity or replenishment rates to avoid over-extraction from any given well or to make most efficient use of the available resources.

[0007] While various systems of the prior art have attempted to address these problems, a possible comprehension of the nature and complexity of the problems inherent in measuring underground resources, such as water or oil, has in many instances led to attempted solutions that are primarily noted for their complexity and cost. The complexity and cost of underground resource monitoring systems of the prior art has, in turn, led to a lack of systems suitable in cost and complexity for monitoring other than high value underground resources, such as water wells as opposed to oil wells.

[0008] The present invention provides a solution to these and other problems of the prior art.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to an apparatus and method for monitoring the status of underground resources or resources that for any reason cannot be directly observed and, in particular, for monitoring resource levels, usage, reserves and trends in one or more water wells of a water system and, for example, alerting users of low water resources and manually or automatically controlling water usage and the operation of water systems according to the availability and recovery rate of water resources and the relative priority of water uses.

[0010] According to the present invention, a well monitoring system for monitoring water resources in a bore having an air column extending from a wellhead to a water surface level and a water column extending from the water surface level to an extraction inlet includes a sensor unit and a base unit. The sensor unit includes a sensor mounted within the bore and including a transmitting unit for transmitting at least a single sound pulse into the bore and a receiving unit for receiving a return signal representing the single sound pulse reflected from the water surface level. The sensor unit also includes a sensor control for controlling the transmission of the single sound pulse and determining a round trip time between transmitting the single sound pulse and receiving the corresponding return signal wherein each single sound pulse has a duration in the range of 20 milliseconds to 50 milliseconds and a transmitted power level in the range of 120 dB, although both the duration and power level may vary widely, depending upon the implementation and the specific circumstances of a given situation.

[0011] The base unit uses the measured round trip time to determine an air column length from the sensor to the water surface level and a water column length from the water surface level to the extraction inlet and, from a cross sectional area of the bore, a water resource value representing a volume of water contained between the water surface level and the extraction inlet.

[0012] The base unit also includes a data memory for storing measurement data values, including the round trip times of a plurality of single sound pulses, and a processor for generating historic resource data values for the well from the plurality of round trip times, including at least one of a current water level, a static water level, a highest recorded water level, a lowest recorded water level, a water level trend, a usage rate, and a recovery rate. The base unit also includes a display for displaying at least one of the water resource value, the current water level, the static water level, the highest recorded water level, the lowest recorded water level, the water level trend, the usage rate, and the recovery rate.

[0013] The base unit further includes a user input for entering at least one alarm limit and storing the alarm limit in the data memory and the processor compares the at least one alarm limit and a corresponding one of a measurement data value and a historic resource data value and generates an alarm signal when the corresponding one of a measurement data value and a historic resource data value concurs with the at least one alarm limit. According to the present invention, an alarm limit may represent one or more of the water resource value, the current water level, the usage rate, and the recovery rate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram of a well monitoring system and a well sensor unit within a well bore;

[0015]FIGS. 2A and 2B are diagrammatic representations of a sound pulse and of a return signal for measuring the level of water in a well;

[0016]FIG. 3 is a block diagram of a generalized water system including a well monitoring system;

[0017]FIG. 4 is a diagram of data measurements obtained from a well monitoring sensor; and,

[0018]FIG. 5 is a block diagram of a monitoring system base unit.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Referring to FIG. 1, therein is a diagrammatic representation of an implementation of the well monitor of the present invention for a single well. As represented therein, a Water System 10 includes a Well 12 having a Bore 14 which is typically defined by a well casing, such as a pipe, in at least in the upper regions of Bore 14. As indicated, the casing typically extends to and above the local ground level and extends downwards as far as required to prevent loose soil and other unwanted contaminates from entering Bore 14. A Wellhead 16 is located at the top of Bore 14 and thereby defines the effective upper extremity of Bore 14 as being the highest point to which Water 18 can rise in Bore 14 without overflowing out of Bore 14. The effective lower extremity of Bore 14 is in turn defined by an Extraction Outlet 20, which is the level at which Water 18 is drawn from Bore 14 and which therefore effectively defines the “bottom” of Well 12 as regards the Water 18 that can be drawn from Well 12.

[0020] In this regard, it will be recognized from the following descriptions that for the purposes of a well monitor of the present invention the Bore 14 need not define or comprise the total diameter or breadth of a Well 12 or other resource to be monitored, but may comprise only a part, and even a small part, of the diameter or breadth of the Well 12. In stead for purposes of the present invention, the Bore 14 defines an enclosed sound channel or sound duct used by the well monitor in transmitting a sound pulse and receiving a return echo, which are used in turn in determining the level of the monitored resource in a Well 12 or in any other resource body. In particular, the Bore 14 serves to guide and channel both the transmitted sound pulse and the return echo, thereby helping to reduce sound loses and allowing most efficient use of the sound pulse power and shielding the monitor from random, incidental or otherwise unwanted echos.

[0021] That is, in many instances, such as in drilled wells, the Bore 14 defines and is the wall of side of the Well 12 and the Bore 14 may be, for example, a pipe lining the Well 12. In other instances, such as a dug well, a tank, a reservoir, a pond or lake, a river or stream or swamp, and so on, the breadth or diameter of the “Well 12” will be larger than that of the Bore 14, and may be significantly larger than the Bore 14. In such instance, the Bore 14 will not be defined by and will not comprise the wall or side of the resource and may be, for example, a metal, concrete, ceramic or plastic pipe suspended or mounted in the resource and extending downwards into the resource.

[0022] It will also be recognized that while the following descriptions will primarily refer to drilled water wells in example and illustration of the present invention, the resource need not be water but may be any other resource providing an acceptable sound reflecting surface, such as oil, brine, or liquified gas or some other compound or substance of interest. In addition, the following discussions will primarily address drilled wells in example and illustration of the present invention, but it will be recognized that the body or container of the resource may include tanks, reservoirs, lakes, ponds, streams, rivers, dug wells, salt domes or caverns, and so on.

[0023] Considering a typical and exemplary implementation of the present invention for monitoring a water well and, in particular, a drilled water well, Bore 14 is filled with a Water Column 22 having an upper surface at current Water Level 24 and an effective current Depth 26 extending from current Water Level 24 to Extraction Outlet 20. Water Column 22 thereby represents the volume of Water 18 that is available to be drawn from Bore 14, exclusive of Replenishment Flow 28 of Water 18 from Sources 30, the nature of which will depend upon the geology and hydrology surrounding Bore 14. As indicated, the remainder of Bore 14 is occupied by an Air Column 32 which, for purposes of the present invention, effectively extends from current Water Level 24 to Wellhead 16 or to the point from which the distance to Water Level 24 is measured, which is often at or close to Wellhead 16.

[0024] Water 18 is typically extracted from Bore 14 by means of Pump 34 and a Piping System 36 extending from Extraction Outlet 20 to a Water Destination 38, which may be, for example, a residence, a community or agricultural water distribution system, and so on. It will be recognized that Piping System 36 may range from a simple delivery pipe, perhaps feeding a pressured distribution/expansion tank, to a complex community, industry or agricultural system. In a like manner, Pump 34 may be located in Bore 14 as illustrated in FIG. 1, or, alternately, and for example, at Wellhead 16. Pump 34 may include or incorporate Extraction Outlet 20, or may be located at any suitable point along the Water 18 flow path. It will be understood that complex Water Systems 10 may include multiple Pumps 34, multiple Extraction Outlets 20 and a complex of Piping System 36.

[0025] A Monitoring System 40 of the present invention and as illustrated in FIG. 1 includes a Sensor Unit 42 and a remote Base Unit 44 communicating with the Sensor Unit 42 through a Communications Link 46. As indicated, a Sensor Unit 42 will typically include a Sensor 48 and a Sensor Control 50 wherein Sensor 48 is mounted within Bore 14 while Sensor Control 50 may be located within or outside of Bore 14, but will usually be mounted close to Sensor 48. Sensor 48 will typically be mounted at or near Wellhead 16, but as will be apparent from the following description of the present invention, may be mounted at any point along Bore 14 so long as Sensor 48 is mounted in Bore 14 above the highest expected Water Level 24. It will also be understood that for purposes of the present invention Air Column 32 is defined as the distance between Sensor 48 and Water Level 24, so that Air Column 32 will effectively extend from Water Level 24 to Wellhead 16 in those instances wherein Sensor 48 is mounted at or near Wellhead 16.

[0026] In this regard, it is well known and understood in the relevant arts that the diameter of a Bore 14 is typically one of a plurality of standard diameters, which are usually based upon such factors as the diameters of pipe ordinarily used to line or form the Bores 14, the diameters of the various types of drills used to form the Bores 14, and so on. It will be apparent from the following descriptions, however, that the present invention may be implemented for any specific diameter of Bore 14 as the actual interior diameter of a given Bore 14 appears only as a parameter dimension stored in the Monitoring System 40 for the purpose of calculating the cross sectional area of the Bore 14, and the volume of Water Column 22, and that this value may be readily changed for various diameters of Bore 14. It will also be understood that the distance between Sensor 48 and Water Level 24, which determines the effective depths, or lengths, of Air Column 32 as the distance between Sensor 48 and Water Level 24 and that of Water Column 22 as the distance between Water Level 24 and Extraction Outlet 20, may vary significantly. As will be apparent from the following descriptions, however, the distance or range of distances between Sensor 48 and Water Level 24 for a given Well 12 is a primary factor only in determining the maximum repetition rate of a pulse signal used to measure that distance and, in some instances, the necessary signal level, or power.

[0027] Also, it will be recognized that the horizontal dimensions of the “Well 12” need not be identical to those of the Bore 14, such as when the “Well 12” is a tank, reservoir, lake, pond, stream, rivers, dug well, salt dome or cavern, and so on. In such instances the horizontal dimension or dimensions of the “Well 12” will likewise be stored as parameter dimensions stored in the Monitoring System 40 and used to calculate the volume or volumes of the resource for various “Water Levels 24”.

[0028] As illustrated, Sensor 48 includes a Pulse Generator 52 for periodically transmitting a Pulse 54 of sound into Bore 14 and a Receiving Unit 56 for receiving a Return Signal 58, or echo, reflected from the surface of Water Column 22 at Water Level 24. In the presently preferred embodiment, each Pulse 54 is comprised of a pulse having a selected duration and signal level and that is generated at a predetermined repetition interval determined, in one aspect, by the maximum depth of the Well 12 or Bore 14 and, in another aspect, by the expected rate of change of Water Level 24. In addition, the Monitor System 40 will “listen” for a corresponding Return Signal 58, or echo, for a predetermined “listening period” after each Pulse 54. The “listening period” is selected to include the expected return times for the first echo of the corresponding Return Signal 58 from Water Level 24, but to exclude subsequent and unwanted echos that may occur. Exemplary embodiments of Pulses 54 are discussed below, but it will be apparent to those of ordinary skill in the arts that Pulses 54 may be of other waveforms, durations, repetition period, and listening periods so long as the parameters allow sufficiently reliable detection of a return echo of the signal.

[0029] Sensor Control 50 may be implemented as a separate unit from Sensor 48 or may be integrated with Sensor 48 and will include a Pulse Controller 60 for driving Pulse Generator 52 to emit a Pulse 54 of the required waveform and signal levels and at the required intervals. Sensor Control 50 will also include a Pulse Detector 62 for detecting a corresponding Return Signal 58 received by Receiving Unit 56.

[0030] Pulse Detector 62 inter-operates with Pulse Controller 60, as discussed further below, to receive from Pulse Controller 60 a Transmission Time 64 of each Pulse 54. Pulse Detector 62 determines the corresponding Received Time 66 of each corresponding Return Signal 58 and, from the transmitting and receiving times of each Pulse 54, may determine the Round Trip Time 68 between Sensor 48 and Water Level 24. Round Trip Time 68 in turn represents the distance between Sensor 48 and Water Level 24 for a given speed of sound in air, which in turn is dependent upon such factors as temperature and pressure.

[0031] The range of possible Round Trip Times 68 for a particular Air Column 32 will depend upon such factors as the speed of sound, the location of Sensor 48 in Bore 14, such as whether Sensor 48 is located at Wellhead 16 or at some depth within Bore 14, and the location of Water Level 24 in Bore 14 at the time a measurement is made. Also, it is desired in the presently preferred implementation of a Well Monitoring System 40 to make each Round Trip Time 68 measurement by means of a single Pulse 54. This in turn requires that Pulse Detector 62 reliably detect a single Return Signal 58, that is, a single returning echo of Pulse 54, and that Pulse Detector 62 be able to determine the Round Trip Time 68 with sufficient accuracy that the Monitoring System 40 can determine the location of Water Level 24 to within, for example, 1 foot. The detection of the Return Signal 58 corresponding to a given Pulse 54 is in turn dependent upon such factors as ambient noise in Bore 14, the duration, shape and frequency, and repetition rate of Pulses 54, the maximum expected distance to Water Level 24, and the diameter of Bore 14. Such factors as Return Signal 58 signal strength, distortion of the original shape, duration and frequency of Pulse 54 and the presence or absence of secondary echos and their signal strengths all also effect the ability of Pulse Detector 62 to accurately detect a Return Signal 58.

[0032] It has been found that a Pulse 54 comprised of a pulse of a selected duration and signal level will provide Return Signals 58 having characteristics such that Pulse Detector 62 can determine the arrival time of a Return Signal 58 with the desired level of accuracy and reliability in a typical water well in a typical Bore 14 or Well 12 setting. These results are in contrast to much experience of the prior art, which has indicated that relatively complex signal waveforms and signal processing are necessary to determine measurements of any nature in a well bore. The signal characteristics of Pulses 54 and Return Signals 58 in turn allows a Monitoring System 40 to be implemented with relatively inexpensive signal generating and processing circuitry, thereby significantly reducing the cost of and increasing the reliability and durability of a Monitoring System 40.

[0033] Examples of typical Pulses 54 and Return Signals 58 are illustrated in FIGS. 2A and 2B wherein FIG. 2A illustrates a sequence of Pulses 54 as transmitted by Pulse Generator 52 and FIG. 2B illustrates a corresponding Return Signal 58. As shown in FIG. 2A and for a typical preferred embodiment of a Monitoring System 40, each Pulse 54 is comprised of pulse having a width, or duration, in the approximate range of 0.009 seconds to 0.031 seconds, a peak amplitude of approximately 0.41 dB and a range of approximately 120 dB. It must be recognized, however, that the power level and range of power levels may vary widely, depending, for example, on the circumstances of a particular implementation of the invention and of a given Bore 14. As illustrated in FIG. 2A, therefore, a Pulse 54 effectively appears as a short pulse or spike having steep rising and falling edges such as is sometimes described as an “impulse”, or as a pulsed generally sinusoidal waveform. FIG. 2B, in turn, illustrates Return Signals 58 resulting from a sequence of Pulses 54 having a Repetition Interval 54RI, wherein each Return Signal 58 is shown as including a Primary Echo 58PE, which is the first echo of the Pulse 54 returned from the water surface at Water Level 24, and at least one Secondary Echo 58SE, which may be, for example, a return echo from two round trips of the Pulse 54 through Air Column 32 or a Pulse 54 return echo from, for example, the actual physical bottom of the Well 12 or Bore 14. As illustrated, the Listening Period 58LP is selected or controlled to include the Primary Echo 58P while excluding, or gating out, any Secondary Echos 58SE.

[0034] As described, the interval between Pulses 54 is typically calculated to be at least twice the time required for a Pulse 54 to traverse Bore 14 between Sensor 48 and Extraction Outlet 20 but no more than is necessary to accommodate the expected rates of change of Water Level 24, thereby allowing maximum efficiency in determining Water Levels 24 in a typical range of Wells 12. The Pulse 54 repetition rate is thereby and typically on the order of 1 minute and is selected, together with the signal level and pulse width, to provide a balance between allowing the greatest reasonable maximum Round Trip Time 68, thus allowing measurements to the maximum typically expected range of depths, the need to have a Return Signal 58, that is, a return echo from the surface of Water Column 22 at Water Level 24, of sufficient amplitude for reliable single pulse detection and time of arrival measurement of a Return Signal 58 by the detection of the highest peak of the Return Signal 58, and the expected “data rate” in terms of rate of change of Water Level 24. In a present implementation, for example, the repetition rate and signal level allow the reliable measurement of the distance from Sensor 48 to Water Level 24 in a range of 5 feet to 2186 feet, assuming a year round average Bore 14 air temperature of 45° F. and a speed of sound in the Bore 14 air of 1093 feet per second (fps).

[0035] In addition, and as described, Pulse Detector 62 “listens” for a Return Signal 58 pulse corresponding to the corresponding Pulse 54 for a “listening period” that will typically have a maximum duration or period selected to be at least the expected maximum time required to receive the first return echo of the Pulse 54 in the Return Signal 58, but no longer than necessary. Appropriate selection or control of the “listening time” will thereby allow the capture of the first Pulse 54 echo from Water Level 24 but will exclude, to the extent possible, all other random, incidental, extraneous, secondary or otherwise unwanted echos. For example, Listening Period 58LP may be of a fixed duration or period selected to be no approximately twice the time required for a Pulse 54 to traverse Bore 14 between Sensor 48 and Extraction Outlet 20. This method, however, may result in “listening to” Secondary Echos 58SE or other unwanted signals for certain Water Levels 24, that is, when the Water Level 24 is such that a Secondary Echo 58SE returns during the listening period. In other implementations, the Listening Period 58LP may be terminated upon detection of the Primary Echo 58P, thereby automatically excluding Secondary Echos 58SE and other unwanted signals. In yet other implementations the start and ending or the ending of Listening Period 58LP may be adjusted to track the actual and predicted occurrence of Primary Echo 58P.

[0036] In this regard, and as mentioned briefly, Pulses 54 having pulse widths in the range of 20 milliseconds to 50 milliseconds, signal levels in the range of 120 dB and repetition rates in the range of 1 second to 6 seconds have yielded satisfactory experimental results in a range of typical Wells 12. Other frequencies, pulse durations and pulse amplitudes may be determined by experiment for particular situations, however, and it should be noted that many conventional and standard integrated circuits providing the functions of Pulse Controller 60 have the capability of generating signals or pulses over a range of frequencies.

[0037] Pulse Detector 62 also determines the current ambient noise level in Bore 14 to determine whether the ambient noise level is too high for reliable detection of the highest peak of the Return Signals 58. In the present embodiment, Pulse Detector 62 monitors and determines the average ambient signal level received by Receiving Unit 56 during the periods between or before the transmissions of Pulses 54, and thereby determines a Noise Level 70 measurement representing the current average ambient noise level in Bore 14. It will be recognized that the ambient “noise” in Bore 14 may be from any of a wide variety of sources, most of which will be of a temporary nature, such as local tools or machines, road traffic, and so on, so that a delay in executing the water level measurements will avoid the effects of noise.

[0038] Pulse Detector 62 will transmit the results of Round Trip Time 68 measurements, and the Noise Level 70 measurements when necessary, to a Base Unit 44 through a Communications Link 46. The data will be transmitted on a periodic basis, such as after each Round Trip Time 68 measurement by the Sensor Unit 42, and the contents of each data transmission, such as whether Noise Level 70 measurements should be communicated to the Base Unit 44, will depend upon the specific configuration of functions in the Monitoring System 40. For example, if the primary control for transmission of Pulses 54 resides in Pulse Controller 60, Noise Level 70 may be used within Sensor Unit 42 to determine whether Pulse Controller 60 should perform a Round Trip Time 68 measurement at a given time or should delay the measurement until a satisfactory noise level is detected, thereby conserving power and the operational life of the pulse transmitting and receiving elements. In this instance, the Noise Level 70 measurements will not be transmitted to Base Unit 44 whereas, if the Base Unit 44 controls or initiates each transmission of a Pulse 54, it may be necessary to communicate the Noise Level 70 measurements, or at least an indication or representation of the presence of noise, or of the presence of noise above or below a predetermined threshold, to the Base Unit 44.

[0039] As illustrated in FIG. 3, a given Monitoring System 40 may include a plurality of Bores l4 and Sensor Units 42 connected from a single Base Unit 44 or a single Bore 14 may include a plurality of Sensor Units 42, so that there may be a single Base Unit 44 for a plurality of Sensor Units 42. In yet other instances, there may be a two or more Bores 14 in sufficiently close proximity that there may be interference or confusion between the Pulses 54 transmitted in the respective Bores 14. As a result, it may be necessary to coordinate or synchronize the operations of two or more Sensor Units 42 to avoid mutual interference, conflict or confusion, either between Data Transmissions 72 to a Base Unit 44 or between the Pulses 54 of various Sensor Units 42.

[0040] The operation of a plurality of Sensor Units 42 in a Monitoring System 40, whether connected to a single Base Unit 44 or to multiple Base Units 44, may be coordinated in a number of ways well known in the art. For example, a Base Unit 44 connected to a number of Sensor Units 42 may control the measurement operations of the Sensor Units 42, that is, the transmission of Pulses 54, by individually keying the transmission of Pulses 54 by the Base Units 44, such as by transmitting individually keyed or addressed Interrogation Signals 74 to the Sensor Units 42. Alternately, the Sensor Units 42 may coordinate their own operations by means of synchronizing signals transmitted from each Sensor Unit 42 to the other Sensor Units 42 using, for example, any of a variety of bus access synchronization methods. In a like manner, the transmission of Data Transmissions 72 from Sensor Units 42 to a Base Unit 44 may be controlled through Interrogation Signals 74 from the Base Unit 44 and addressed to the individual Sensor Units 42 or by self-synchronization among the Sensor Units 42.

[0041] It will also be recognized that the contents of Data Transmissions 72 will depend upon the specific configuration and implementation of a Monitoring System 40. For example, and as illustrated in FIGS. 3 and 4, in a system having a single Sensor Unit 42 and a single Base Unit 44 the Data Transmissions 72 may contain only Measurement Data 76 wherein Measurement Data 76 is comprised of various measurements made by the Sensor Unit 42 and which are of use in determining or calculating the desired data regarding water resources. As discussed herein above, the principle Measurement Data 76 parameter will typically be the measurement of the distance between Sensor 48 and Water Level 24. As discussed, this distance may be represented by a measurement or count of Round Trip Time 68 or, in those implementations wherein the Round Trip Time 68 is converted into a distance measurement in the Sensor Unit 48, a value directly representing the distance between the Sensor 48 and the Water Level 24. In further implementations of the present invention, and for example, Measurement Data 76 may include a Noise Level 70 measurement in those systems wherein the Base Unit 44 controls the transmission of Pulses 54, or a measurement of the actual temperature in the Bore 14 in instances where greater accuracy is desired in determining the distance between Sensor 48 and Water Level 24. or in the form of a distance measurement, wherein the Pulse Detector 62 converts each Round Trip Time 68 measurement into a corresponding distance measure. In certain implementations, and in particular in implementations having multiple Sensor Units 42, each Data Transmission 72 may also include a Sensor Unit Identifier 78 identifying the specific Sensor Unit 42 that is the source of the Data Transmission 72.

[0042] Data Transmissions 72, Interrogation Signals 74 and other communications between a Base Unit 44 and Sensor Units 42 are communicated through Communications Link 46, which may be, for example, a radio link, an infra-red link or a direct wire connection. For this reason, Base Unit 44 and Sensor Units 42 may include, respectively, a Base Transceiver 80 and a Sensor Transceiver 82 appropriate to the nature of Communications Link 46. As such Communications Links 46, Base Transceivers 80 and Sensor Transceivers 82 are will known in the arts, Communications Links 46 and the implementations thereof will not be discussed further herein.

[0043] Lastly with regard to Sensor Units 42, and as illustrated in FIG. 1, each Sensor Unit 42 will include a Power Unit 84 and that Power Units 84 may be of any of a wide variety of types of power sources, or even combinations of power sources. For example, a Power Unit 84 may be comprised of batteries, solar cells, solar cells charging batteries, a direct ac power connection, or a power connection from a Base Unit 44.

[0044] Considering Base Unit 44 as illustrated in FIG. 5 in further detail, certain data processing may be performed in Sensor Units 42 when advantageous, such as the conversion between Round Trip Time 68 and the length of an Air Column 32, as this calculation requires only a stored constant, that is, the average speed of sound in a Bore 14, and the Round Trip Time 68, which is measured by the Sensor Unit 42 itself. Others of the calculations, however, such as determining the volume of currently available water resources and the replenishment and draw-down rates, historical trends, and so on, require data that is most conveniently and efficiently stored in the Base Unit 44 and the results of the calculations are typically displayed at the Base Unit 44. These calculations and the display of the results are thereby more efficiently performed at the Base Unit 44 rather than in the Sensor Units 42 and, in the presently preferred embodiments of a Monitoring System 40, the majority of data processing is thereby typically performed in Base Unit 44, thereby reducing the cost and complexity of Sensor Units 42, which may be more numerous than Base Units 44.

[0045] As indicated in FIG. 5, the Measurement Data 86 for each associated Sensor Unit 42, such as Round Trip Time 68, is stored in a Data Memory 88 together with Bore Parameters 90, such as Bore Diameter 92. Bore Parameters 90 include parameters that pertain to Bore 14 or the environment therein and that are used in calculating or generation the desired resource information for the Bore 14, such as the current volume of available water, but which are essentially constant values over time and are not the result of the individual measurements of current conditions in the Bore 14, such as Round Trip Times 68. For example, Bore Parameters 90 will typically include a Bore Diameter 92, which is the inner diameter of Bore 14 and which defines the circular area of Water Level 24 and which in turn and together with the length of Water Column 22 will determine the extractable volume of water currently present in Water Column 22. Bore Parameters 90 may also include, for example, a parameter representing the speed of sound in Air Column 32, which is used in determining Water Level 24, a parameter representing the depths, or locations, of Extraction Outlet 20 and Sensor Unit 48 in Bore 14, and so on. Bore Parameters 90 will not include those parameters resulting from current measurement data, such as Measurement Data 86, and which may typically vary from measurement to measurement. Bore Parameters 90 are thereby relatively constant values and may be stored in a Base Unit 44 during manufacture, at an initial setup of a Monitoring System 40, or by a user.

[0046] Bore Parameters 90 and Measurement Data 86 are operated upon according to processes executed by Processing Unit 94, and the resulting Calculated Water Resource Data 96, such as the volume currently available water resources, replenishment and draw-down rates, historical trends, and so on. Calculated Resource Data 94 is also stored in Data Memory 88, and it should be noted that certain of Calculated Water Resource Data 96, such as the volume of water in Water Column 22 at various points in time may be used in generating further Calculated Water Resource Data 96, such as the rate of extraction and replenishment, and so on.

[0047] That is, and for example, the extractable volume of Water 18 in Bore 14 is comprised of the volume of Water 18 between Water Level 24 and Extraction Outlet 20 and is dependent upon Bore Diameter 92. In order to determine the extractable volume of Water 18, therefore, Bore Parameters 90 will include a Bore Length 98, which is defined as the distance between Sensor 48 and Extraction Outlet 20. Bore Length 98 thereby represents the effective maximum possible length of Water Column 22, if the Water Level 24 has risen to Sensor 48, or the maximum possible length of Air Column 32, if the well has been pumped down so that Water Level 24 is at Extraction Outlet 20. Round Trip Time 68 measurement represents the distance between Sensor 48 and Water Level 24 for a given speed of sound in air, and thereby is a measure and representation of the length of Air Column 32. The difference between Bore Length 98 and the length of Air Column 32 is therefore the length of Water Column 22.

[0048] The product of the length of Water Column 22 and the circular area of Water Level 24, which is calculated from Bore Diameter 92, which is a stored Bore Parameter 90, is the Resource Volume 100 of Water 18 between Water Level 24 and Extraction Outlet 20, that is, the volume of Water 18 that can be extracted from Bore 14, exclusive of Replenishment Flow 28 and assuming a constant Bore Diameter 92 along the depth of Bore 14. As described, Resource Volume 100 is stored in Data Memory 88 as an element of Calculated Water Resource Data 96. In this regard, and in further example, it should be noted that a Bore 14 need not in fact have a constant Bore Diameter 92 throughout its depth, but may have a varying bore diameter. The determination of Resource Volume 100, however, will be straightforward except that the depths, lengths and diameters of the various sections of Bore 14 will be stored in Data Memory 88 as stored Bore Parameters 90 and the dimensions of the various bore segments comprising Water Column 32 will be determined for different depths of Water Level 24 as Water Level 24 moves up and down in Bore 14.

[0049] As described, other Calculated Water Resource Data 96 may be in turn generated from such Calculated Water Resource Data 96 as Resource Volume 100. For example, in a present embodiment of a Base Unit 44 the Calculated Water Resource Data 96 generated by Processing Unit 90 and stored in Data Memory 88 and displayed through a Display 102 may include, for example and for each Sensor 48 connected from the Base Unit 44:

[0050] a Resource Volume 100 (current volume of water that may be extracted —determined as (Bore Length 98—the length of Air Column 32)×(circular area of Water Level 24)),

[0051] Current Water Level 24 (determined as Bore Length 98—the length of Air Column 32),

[0052] Highest Recorded Water Level 104 (maximum recorded historical value of Current Water Level 24),

[0053] Lowest Recorded Water Level 106 (minimum recorded historical value of Current Water Level 24),

[0054] Static Level 108 (the steady state level that Water Level 24 will assume when Water 18 is not being extracted from the Bore 14 and after Replenishment Flow 28 has refilled Water Level 24 to the Static Level 108; in some circumstances Static Level 108 may represent the “ground water level” and in other circumstances Static Level 108 may represent the highest level of a water vein feeding the Bore 14),

[0055] Recovery Rate 110 (change in Resource Volume 100 over a defined period while Water 18 is not being drawn from Well 12, or the time needed for Water Level 24 to return to Static Level 108),

[0056] Trend 112 (the direction and rate or amount of change in Water Level 24 or Resource Volume 100 over a predetermined time interval),

[0057] Usage Rate 114 (decrease in Resource Volume 100 over a defined period while Water 18 is being drawn from Well 12),

[0058] and so on.

[0059] The calculation of such Calculated Water Resource Data 96 from the information discussed herein above will be apparent to those of ordinary skill in the relevant arts and, as such, need not be discussed further herein.

[0060] In the presently preferred embodiments of the present invention, a Base Unit 44 will provide further Well 12 monitoring and control functions, many of which will be based upon the Calculated Water Resource Data 96 or related to the tracking and use of Calculated Water Resource Data 96.

[0061] For example, in Water System 10 having multiple Bores 14, each with a Sensor Unit 42, or having multiple Sensor Units 42 for any reason, a user may enter one or more corresponding Bore Identifications 118, each corresponding to a Sensor Unit 42, to organize Calculated Water Resource Data 96 and the corresponding Measurement Data 86 from the Sensor Units 42 accordingly. Depending upon the specific details of an implementation of a Monitoring System 40, a Bore Identification 118 may be stored in Memory 88 to organize the data stored therein and may be uploaded or transferred to the corresponding Sensor Unit 42 to be used in identifying Measurement Data 86 transmitted from that Sensor Unit 42. In other implementations, a Bore Identification 118 may be entered directly into a Sensor Unit 42 or may be wired into the Sensor Unit 42 and may be detected by the Base Unit 44, for example, at system initialization or system calibration.

[0062] In functions more directly related to Calculated Water Resource Data 96, a user may enter an Alarm Limit 120 identifying, for example, a lower limit for Water Level 24, a lower limit for Resource Level 98 or a lower limit for Recovery Rate 110, each representing a lower limit value below which the water level or available water volume should not be drawn or warning of an unacceptably slow recovery rate. Processing Unit 90 will compare the appropriate one of the current Water Level 24, the current Resource Level 98 or the Recovery Rate 110 with the Alarm Limit 120 and may generate a corresponding Alarm Output 122, which may be visual or audible or both, if the current Water Level 24, Resource Level 98 or Recovery Rate 110 decreases down to the Alarm Limit 114 for any other reason.

[0063] It should be noted that in other implementations the Alarm Limit 120 value may be set by Processor 90 as a percentage of, for example, the Current Water Level 24, Highest Recorded Water Level 104, or Lowest Recorded Water Level 106, and that the Alarm Limit 120 value may be set or modified as a function of the current Recovery Rate 110, Trend 112 or Usage Rate 114. Also, equivalent Alarms Limits 120 may be set for such values as the current Recovery Rate 110, Trend 112 or Usage Rate 114. In yet other implementations, and for example, a Safe Level Indicator 124 may be set and triggered when, for example, the current Water Level 24, Resource Level 98 or Recovery Rate 110 rises to a given level, thereby indicating that the Bore 14 is at an adequate capacity and ready for use again, or is recovering at a safe rate.

[0064] It should also be noted that an Alarm Output 122 may control functions of a Water System 10 beyond providing an alarm indication. For example, an Alarm Output 122 may provide a signal to turn off a pump or valve, thereby halting the draw of water from a well, and a Safe Level Indication 124 may restart the pump or open the valve so that water can continue to be drawn from the Bore 14. In other instances, the operation of an Alarm Output 122 or a Safe Level Indication 124 may be proportional. That is, and rather than providing merely an on/off control, the actual resource values may be compared to the alarm levels and the rate or volume of draw from a well adjusted accordingly so as, for example, to provide or allow a maximum sustainable continuous flow of water. In other instances, and in particular in systems having multiple Bores 14, a Base Unit 44 may control the proportionate draw of water from each Bore 14 or may transfer the draw load among the Bores 14 to provide or allow, for example, a maximum sustainable continuous flow of water from the system.

[0065] Referring again to Display 102, in presently preferred embodiments Display 102 may be, for example, a liquid crystal (LCD) type display having selectable display areas for each data item to be displayed to a user, such as current Water Level 24, Resource Volume 100, Highest Recorded Water Level 104, Lowest Recorded Water Level 106, Static Level 108, Recovery Rate 110, Trend 112, Usage Rate 114, Alarm Limits 120, and so on. Such a Display 102 will typically be capable of generating graphic displays as well as alphanumeric displays and, as illustrated, may present certain of the Calculated Water Resource Data 96, such as current Water Level 24, Highest Recorded Water Level 104 and Lowest Recorded Water Level 106, Recovery Rate 110 and Trend 112 in graphic form. A Display 102 with such functionality, and which may include touchscreen input capabilities, will also display and provide User Inputs 126 by which a user may enter, for example, Alarm Limits 114, Bore Information 90, Bore Identifiers 118, other relevant well parameters for set-up and calibration of the system, and so on. The uses of such LCD and touchscreen displays and well known in the art, however, and need not be described in further detail herein.

[0066] It will also be recognized that a Display 102 with an associated user input may also be comprised of, for example, a personal computer connected to a Base Unit 44, either permanently or as needed, a computer operating through a network, a monitor and keyboard unit at each Base Unit 44, or any of a variety of hand held units, such as personal digital assistants, some cell phone, and other handheld communications and computing devices.

[0067] Lastly with regard to Base Units 44, it will be noted that each Base Unit 44 will include a Power Unit 128 and that Power Units 128 may be of any of a wide variety of types of power sources, or even combinations of power sources. For example, a Power Unit 128 may be comprised of batteries, solar cells, solar cells charging batteries, a direct ac power connection and ac to dc power supply, a dc power connection from a central power supply, and so on.

[0068] Since certain changes may be made in the above described invention, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention. For example, in Wells 12 having large diameter Bores 14, such as dug wells, reservoirs or tanks, a Bore 14 comprised, for example, of a piece of piping or tubing communicating freely with the water or other resource in the well, reservoir or tank may be inserted into the well, with the Sensor Unit 42 mounted at the top thereof, to provide a constrained Bore 14 serving as a sound channel for the transmission and reception of Pulses 54 and Return Signals 58. It will thereby be recognized that the present invention may be employed to monitor resource levels in situations other than drilled wells, such as dug or excavated wells, tanks, reservoirs, rivers, lakes and streams, and so on. It will also be recognized that virtually any material may be used for Bore 14, such as piping or tubing, including steel or iron, corrugated metals, and plastic, such as PVC piping. It must also be recognized that a monitoring system of the present invention may be used to monitor resources other than water, such as brine, salt water, oil, liquified gases or other liquids, so long as the monitored resource provides a reflecting surface or interface to return a Return Signal 58 in response to a Pulse 54 

What is claimed is:
 1. A well monitoring system for monitoring water resources in a bore having an air column extending from a wellhead to a water surface level and a water column extending from the water surface level to an extraction inlet, comprising: a sensor unit including, a sensor mounted within the bore and including a transmitting unit for transmitting at least a single sound pulse into the bore and a receiving unit for receiving a return signal representing the single sound pulse reflected from the water surface level, and a sensor control for controlling the transmission of the single sound pulse and determining a round trip time between transmitting the single sound pulse and receiving the corresponding return signal, each single sound pulse having a duration in the range of 20 milliseconds to 50 milliseconds, a base unit for determining, from the round trip time, an air column length from the sensor to the water surface level and a water column length from the water surface level to the extraction inlet, and from a cross sectional area of the bore, a water resource value representing a volume of water contained between the water surface level and the extraction inlet.
 2. The well monitoring system of claim 1, the base unit further including: a data memory for storing measurement data values including the round trip times of a plurality of single sound pulses, a processor for generating historic resource data values for the well from the plurality of round trip times, including at least one of a current water level, a static water level, a highest recorded water level, a lowest recorded water level, a water level trend, a usage rate, and a recovery rate, and a display for displaying at least one of the water resource value, the current water level, the static water level, the highest recorded water level, the lowest recorded water level, the water level trend, the usage rate, and the recovery rate.
 3. The well monitoring system of claim 2, the base unit further including: a user input for entering at least one alarm limit, the data memory for storing the at least one alarm limit, and the processor for comparing the at least one alarm limit and a corresponding one of a measurement data value and a historic resource data value and generating an alarm signal when the corresponding one of a measurement data value and a historic resource data value concurs with the at least one alarm limit.
 4. The well monitoring system of claim 3, wherein the at least one alarm limit represents one of: the water resource value, the current water level, the usage rate, and the recovery rate.
 5. The well monitoring system of claim 1, wherein each single sound pulse is a pulsed sinusoidal signal.
 6. A method for monitoring water resources in a well bore having an air column extending from a wellhead to a water surface level and a water column extending from the water surface level to an extraction inlet, comprising: transmitting from the wellhead and into the bore at least a single sound pulse and receiving a return signal representing a reflection of the single sound pulse from the water surface level, and determining a round trip time between transmitting the single sound pulse and receiving the corresponding return signal, each single sound pulse having a duration in the range of 20 milliseconds to 50 milliseconds, and from the round trip time, determining an air column length from the wellhead to the water surface level and a water column length from the water surface level to the extraction inlet, and from a cross sectional area of the bore, determining a water resource value representing a volume of water contained between the water surface level and the extraction inlet.
 7. The well monitoring method of claim 6, further comprising the steps of: storing measurement data values including the round trip times of a plurality of single sound pulses, and generating historic resource data values for the well from the plurality of round trip times, including at least one of a current water level, a static water level, a highest recorded water level, a lowest recorded water level, a water level trend, a usage rate, and a recovery rate, and displaying the at least one of the water resource value, the current water level, the highest recorded water level, the lowest recorded water level, the water level trend, the usage rate, and the recovery rate.
 8. The well monitoring method of claim 7, further including the steps of: determining at least one alarm limit, and comparing the at least one alarm limit and a corresponding one of a measurement data value and a historic resource data value and generating an alarm signal when the corresponding one of a measurement data value and a historic resource data value concurs with the at least one alarm limit.
 9. The well monitoring system of claim 8, wherein the at least one alarm limit represents one of: the water resource value, the current water level, the usage rate, and the recovery rate.
 10. The well monitoring system of claim 6, wherein each single sound pulse is a pulsed sinusoidal signal.
 11. A monitoring system for monitoring a resource in a bore having an air column extending to a resource surface level and a resource column extending from the surface level to an extraction inlet, comprising: a sensor unit including, a sensor mounted within the bore and including a transmitting unit for transmitting at least a single sound pulse into the bore and a receiving unit for receiving a return signal representing the single sound pulse reflected from the resource surface level, and a sensor control for controlling the transmission of the single sound pulse and determining a round trip time between transmitting the single sound pulse and receiving the corresponding return signal, each single sound pulse having a duration in the range of 20 milliseconds to 50 milliseconds, a base unit for determining, from the round trip time, an air column length from the sensor to the resource surface level and a resource column length from the resource surface level to the extraction inlet, and from a cross sectional area of the bore, a resource value representing a volume of the resource contained between the surface level and the extraction inlet.
 12. A method for monitoring resources in a bore having an air column extending to a resource surface level and a resource column extending from the resource surface level to an extraction inlet, comprising: transmitting at least a single sound pulse into the bore and receiving a return signal representing a reflection of the single sound pulse from the resource surface level, and determining a round trip time between transmitting the single sound pulse and receiving the corresponding return signal, each single sound pulse having a duration in the range of 20 milliseconds to 50 milliseconds, and from the round trip time, determining an air column length to the resource surface level and a resource column length from the resource surface level to the extraction inlet, and from a cross sectional area of the bore, determining a resource value representing a volume of resource contained between the resource surface level and the extraction inlet. 